The aim of this study is to develop and investigate mechanical properties of knitted unidirectional thermoplastic composite prepregs. Knitted prepregs were fabricated by using thermoplastic yarns (high density polyethylene and polypropylene) and high performance yarns (kevlar, basalt and carbon) in double jersey inlay structure. This is a new approach to combine the reinforcing fiber with resin forming thermoplastic fiber during the knitting operation. The structures were stacked further in three stacking sequences at different angles (0/0/0/0, 0/90/0/90, 0/90/90/0), and hot compression was used to convert them into composite prepregs by melting the thermoplastic component. Mechanical properties e.g. tensile strength and modulus, flexural strength, flexural modulus, impact energy absorbed etc. were investigated in detail. Full factorial experimental design was used in order to study the effect of main yarn, inlay yarn and direction of stacking/plying on mechanical properties of composites. Analysis of variance (ANOVA) was conducted by Minitab 17 software to estimate the significance of testing direction (T), type of inlay yarn (I), type of main yarn (M) and stacking sequence (S) on mechanical properties. Overall highest tensile and flexural strengths were observed for Carbon fiber based samples followed by Kevlar and Basalt respectively. Theoretical estimation of elastic modulus shows similar trend as the experimental results. The inter-laminar shear strength is maximum when the fiber orientation changes in each layer. Type of main yarn and inlay yarn have significant contribution on impact related properties. Depending upon type of material, these composites can be used in aerospace, automotive, civil and sports goods.
Mitigation of electromagnetic interference (EMI) through thin, lightweight, and cost-effective materials is critical for electronic appliances as well as human health. The present research work discusses the design of composites that are suitable to minimize EMI through various stacking sequences. The carbon fibers reinforced composite structures impregnated with dielectric (MWCNTs) and magnetic nanofillers (Fe2O3) were developed to investigate their microwave absorption properties. The composite structure comprising a single type of nanofillers each of MWCNTs & Fe2O3 was developed and then their layers were stacked over each other with various stacking sequences to investigate the best stacking sequence which presents good microwave absorption characteristics. A vector network analyzer (VNA) was used to analyze the microwave absorption properties of these developed composite structures. The composite structures impregnated with the layers of dielectric nanofiller and sandwiched between the layers of a magnetic nanofiller show the highest EMI shielding value of 59 dB and a dielectric conductivity of 35 S/cm in the frequency range of 0.1 to 13.6 GHz. The results also demonstrate that the microwave absorption properties of the developed composite structures were dominant over reflection properties. The absence of an external peak in X-ray diffraction (XRD), marked the purity of the added nanofillers.
Auxetic materials have negative Poisson ratio which has a multiple ranges of functional applications. The helical auxetic yarn was successfully developed through direct twist system by using core and wrap yarn or filament, which shows Auxeticity when the HAY is stretched in longitudinal direction in response it expand in transverse direction, Helical Auxetic Yarns were developed using various parameters of the core and warp filament, these parameters are wrapping angle (Twist per meter), diameter ratio, and modulus ratio. The strength of Helical yarn was characterized using single yarn strength and Image J software was used for the calculation of poisson’s ratio. According to test results, it is concluded that the core filament of helical auxetic yarn increased its thickness in transverse direction under stress, and a considerable negative poisson’s ratio was calculated. The values of negative poisson’s ratio described that the auxeticity had a direct relation with core filament thickness or diameter and inversely proportional to the linear density of wrap filament, in case of the wrap angle the auxeticity of HAY yarn had an inverse effect with wrap angle. Kevlar/polypropylene combination sample showed maximum auxeticity at a 15-degree angle while Kevlar/nylon combination sample showed minimum auxeticity at a 25-degree wrap angle.
This work was aimed to study the mechanical properties of multilayered woven automobile seatbelt by varying the weave design, fabric density and material. Three layered woven webs were produced in three different weaves (twill, matt and combination of plain and matt named here as “combo”). The webs were produced either in polyester, Polyamide (Nylon) or by using combination of both.The seatbelts produced in matt weave were able to bear more load before rupture as compared to twill and combo weaves. The effect of actual thread density and fabric areal densityon the breaking strength of seatbelt was found. Finally, a low cost seat belt having minimum fabric areal density and optimum strength was proposed.
Abstract The Electromagnetic Interference (EMI) shielding characteristics of PVC based nanocomposites were studied when reinforced with newly developed Thermally Reduced Graphene Oxide (TRGO) coated with Polyaniline (PANI) nanoparticles. Various techniques were utilized to characterize prepared nanocomposite films like Scanning Electron Microscopy (SEM), direct current (DC) conductivity measurement, impedance analyses, and EMI shielding. EMI shielding was measured in three different regions of the electromagnetic spectrum like the Microwave region (0.1 GHz to 20 GHz), Near InfraRed (NIR), and Ultraviolet region (UV). The coating of PANI over TRGO provides compatibility of nanoparticles with a polymer matrix that leads to enhanced dispersion. EMI shielding was found to be 104 dB for 40 wt% filler content, because of the formation of a mature and dense interconnected network structure of filler. UV and NIR transmittance was also studied and less than 0.5% transmission in the whole UV (200 nm 400 nm) and NIR (700 nm 2500 nm) region was observed.
Knitted auxetic fabrics (AF) are in common practice but their stability and thickness are major problems in commercial applications. Therefore, a simple method of developing woven AF is proposed here. Differential shrinking property of different weaves is utilized to visualize auxetic honey comb geometry in fabric structure. Based on this fabric structure, auxeticity is induced in 2-D-woven fabric. AF is developed using conventional nonauxetic materials (i.e., cotton in warp and elastane [Lycra] yarn in the weft). Auxetic nature and auxetic structure in the fabric were characterized by microscope. Comfort properties (air permeability, thermal resistance, stiffness, and wicking) of AF were compared with conventional nonauxetic fabrics (NAF). Piezoresistive nature of conductive AF and NAF is also compared. AF showed superior comfort properties and higher sensitivity as compared to conventional NAF. Based on results, AF can be considered better replacement of conventional NAF in wearable and medical applications.
Hydrogels wound dressings have enormous advantages due to their ability to absorb high wound exudate, capacity to load drugs, and provide quick pain relief. The use of hydrogels as wound dressings in their original form is a considerable challenge, as these are difficult to apply on wounds without support. Therefore, the incorporation of polymeric hydrogels with a certain substrate is an emerging field of interest. The present study fabricated cellulose hydrogel using the sol–gel technique and reinforced it with nonwoven cotton for sustainable wound dressing application. The nonwoven cotton was immersed inside the prepared solution of cellulose and heated at 50 °C for 2 h to form cellulose hydrogel–nonwoven cotton composites and characterized for a range of properties. In addition, the prepared hydrogel composite was also loaded with titania particles to attain antibacterial properties. The Fourier transform infrared spectroscopy and scanning electron microscopy confirmed the formation of cellulose hydrogel layers inside the nonwoven cotton structure. The fabricated composite hydrogels showed good moisture management and air permeability, which are essential for comfortable wound healing. The wound exudate testing revealed that the fluid absorptive capacity of cellulose hydrogel nonwoven cotton composite was improved significantly in comparison to pure nonwoven cotton. The results reveal the successful hydrogel formation, having excellent absorbing, antimicrobial, and sustainable properties.
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